JP3500655B2 - Granulation method of fluoropolymer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for granulating a fluorine-containing polymer, and more specifically, it uses a granulating medium that causes less environmental damage, such as heat resistance, solvent resistance and chemical resistance. The present invention relates to a method for efficiently granulating a good fluoropolymer.

[0002]

2. Description of the Related Art Fluorine-containing polymers have heat resistance, solvent resistance,
Since it is a polymer material having excellent chemical resistance, it has been utilized for various purposes by taking advantage of its characteristics.

As a method for producing a fluoropolymer, a solution polymerization method, a suspension polymerization method and an emulsion polymerization method are known. As a polymerization medium for the solution polymerization method or the suspension polymerization method, an inert solvent such as chlorofluorocarbon is usually used from the viewpoints of providing a high molecular weight copolymer and having a high polymerization rate. Specific examples of chlorofluorocarbons include trichlorofluoromethane, dichlorodifluoromethane,
Examples thereof include trichlorotrifluoroethane and dichlorotetrafluoroethane, but trichlorotrifluoroethane is mainly used from the viewpoint of handling. Also,
By contacting the fluorine-containing polymer containing these media with water under stirring, the medium is separated from the fluorine-containing polymer and the fluorine-containing polymer is granulated, and the powder fluidity and molding processability are improved. The method of improvement is conventionally known (Japanese Patent Publication No. 50-17230).

In recent years, ozone layer depletion has been taken up internationally as a global environmental destruction problem, and chlorofluorocarbon has been pointed out as the causative substance thereof, and it is heading for global abolition. For this reason, it has become necessary to stop the use of chlorofluorocarbons when producing a fluoropolymer.

As alternatives to this chlorofluorocarbon, perfluorocarbons and hydrofluorocarbons containing hydrogen atoms have been proposed because they have a small ozone depletion potential.

[0006]

The present invention provides a method for efficiently granulating a fluoropolymer having excellent heat resistance, solvent resistance and chemical resistance without using chlorofluorocarbon having a large ozone depletion potential. The purpose is to provide.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have improved powder fluidity and moldability by using a specific hydrofluorocarbon during granulation. It was found that the granulated product of the fluoropolymer can be efficiently produced.

That is, the present invention is a method for granulating a fluoropolymer having a fluoroolefin unit as a main constituent unit, which comprises C ₄ F ₄ H ₄ , C ₄ F ₈ H ₂ , C ₅ F ₁₁ H, C
₅ F ₁₀ H ₂ , C ₆ F ₁₃ H, C ₆ F ₁₂ H ₂ or C ₆
Separating the hydrofluorocarbon from the fluoropolymer by contacting the fluoropolymer containing the specific hydrofluorocarbon represented by F ₉ H ₅ with water at a temperature of 20 to 150 ° C. under stirring. In addition, there is provided a method for granulating a fluoropolymer, which comprises granulating the fluoropolymer.

The fluoropolymer having a fluoroolefin unit as a main constituent unit in the present invention is a fluoropolymer obtained by polymerizing a fluoroolefin monomer alone or in combination of two or more kinds, or by copolymerizing with a fluoroolefin monomer. It is produced by copolymerizing a monomer other than the olefin monomer.

The fluoroolefin monomer used in the present invention is an olefin having at least one fluorine atom in the molecule, and is preferably carbon in the molecule in view of polymerizability and properties of the resulting polymer. It is a fluoroolefin monomer having 2 or 3 atoms.

Specific examples of such fluoroolefin monomer include CF ₂ ═CF ₂ , CF ₂ ═CFCl, C
F ₂ = fluoroethylene-based monomer such as CH ₂ , CF ₂
Examples include fluoropropylene-based monomers such as ═CFCF ₃ and CF ₂ ═CHCF ₃ . These fluoroolefin monomers may be used alone or in combination of two or more.

Examples of the monomer other than the fluoroolefin monomer copolymerizable with these fluoroolefin monomers include the following. CF ₃ CF ₂ CF ₂ CF ₂ CH = CH ₂ or CF ₃ CF ₂
CF ₂ CF ₂ CF = CH ₂ or other perfluoroalkyl group having 4 to 12 carbon atoms (perfluoroalkyl)
Ethylene monomer. ^{_{R f (OCFXCF 2) m OCF}} = CF 2 ( wherein ^{R f} is a perfluoroalkyl group having 1 to 6 carbon atoms, X is a fluorine atom or a trifluoromethyl group, m represents an integer of 1-6.) Perfluoro vinyl ether type monomers such as. _{CH 3 OC (= O) CF} 2 CF 2 CF 2 OCF = CF 2
And FSO ₂ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF
= A vinyl ether monomer having a group such as CF ₂ that can be easily converted into a carboxylic acid group or a sulfonic acid group. Olefinic monomers such as ethylene, propylene and isobutylene.

A particularly desirable fluoropolymer is a tetrafluoroethylene / ethylene copolymer. As the monomer further copolymerizable with tetrafluoroethylene and ethylene, other than tetrafluoroethylene and ethylene,
Fluoroolefins such as vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, hexafluoropropylene and (perfluoroalkyl) ethylene, fluorovinyl ethers, acrylic acid, methacrylic acid, vinyl chloride and the like can be adopted.

In the present invention, C_FourF_FourH_Four,C _Four F
₈ H _Two , C₅F₁₁H, C₅F₁₀H_Two, C₆F
_ThirteenH, C₆F₁₂H_TwoOr C₆F₉H₅Special represented by
Regular hydrofluorocarbon (hereinafter referred to as "specific HFC")
U ) Is used. Low boiling point unless specified HFC
Too much or the boiling point is too high, and the desired granules are effective.
I can't get it efficiently. Also, there are no hydrogen atoms in the molecule.
No, that is, in the case of perfluorocarbons
Polymer, especially tetrafluoroethylene / ethylene copolymer
The affinity with the coalescence is poor, and the preferred granules cannot be obtained.
When the number of hydrogen atoms in the molecule is greater than the number of fluorine atoms
Also the parent of hydrofluorocarbons and fluoropolymers
The compatibility is poor and a preferable granulated product cannot be obtained. In particular
The following is exemplified. 1,1,2,2-tetrafluorocyclobutane, CF_Two
HCF_TwoCF_TwoCF_TwoH, CF_ThreeCFHCF_TwoCF_TwoC
F_Three, CF_ThreeCF_TwoCF_TwoCF_TwoCF_TwoH, CF_ThreeCF
_TwoCFHCF_TwoCF_Three, CF_ThreeCFHCFHCF_TwoCF
_Three, CF_TwoHCF_TwoCF_TwoCF_TwoCF_TwoH, CF_TwoHC
FHCF_TwoCF_TwoCF_Three, CF_ThreeCF_TwoCF_TwoCF_TwoC
F_TwoCF_TwoH, CF_ThreeCH (CF_Three) CF_TwoCF_TwoCF
_Three, CF_ThreeCF (CF_Three) CFHCF_TwoCF_Three, CF_Three
CF (CF_Three) CFHCFHCF_Three, CF_ThreeCH (CF
_Three) CFHCF_TwoCF_Three, CF_TwoHCF_TwoCF_TwoCF_Two
CF_TwoCF_TwoH, CF_ThreeCF_TwoCF_TwoCF_TwoCH_TwoCH
_Three. Whether the specific HFC is the same as or different from the polymerization medium
Good.

The amount of the specific HFC contained in the fluoropolymer is not particularly limited, but if it is too small, the action and effect of the present invention cannot be sufficiently achieved, and if it is too large, there is no influence on the action and effect. It is not preferable from the viewpoints of economics, processing equipment, and work. Usually, the amount of the specific HFC present during the contact treatment with water is 50 parts by weight or more, preferably about 100 to 3000 parts by weight, particularly about 1000 to 2500 parts by weight, based on 100 parts by weight of the fluoropolymer. It

The amount of water used in the contact treatment is not particularly limited, but is preferably about 50 to 500% by volume with respect to the total amount of the specific HFC and the fluoropolymer. In the present invention, the temperature at the time of contact treatment with water is important and is 20 to 15
Good results are obtained at temperatures in the range of 0 ° C. The optimum temperature is appropriately selected according to the type and amount of the specific HFC, the contact treatment time, etc., and is particularly preferably about 30 to 100 ° C. If the temperature is too low, generally, a long treatment time is required, and it becomes difficult to obtain good results in terms of action and effect. When the temperature is too high, the pressure in the system becomes high, the operability is deteriorated, and the properties of the fluoropolymer may be deteriorated. The treatment time is usually about 15 minutes to 30 hours in the above temperature range, and at least a sufficient time is required to separate the specific HFC.

The contact treatment with water in the present invention is usually carried out in a treatment apparatus equipped with a stirring blade under the above-mentioned conditions under the specified HFC.
It is carried out by stirring and mixing the fluoropolymer containing water and water. As the processing device, a normal stirring tank or a stirring tank with a baffle plate may be used. Further, as the stirring blade, a commonly used stirring blade such as a turbine blade or a chi-type blade can provide good results. The fluorine-containing polymer containing the specific HFC has no compatibility with water and has a high density, and therefore sinks to the bottom of the tank.
Further, the granulated product of the fluoropolymer after the specific HFC is separated floats on the water surface. Therefore, the contact condition between the fluoropolymer and water is appropriately set within the optimum range depending on the mixing ratio of the fluoropolymer, the specific HFC and water, and the like.

The particle size of the granulated product of the fluoropolymer according to the present invention can be appropriately changed depending on the initial stirring conditions in which the specific HFC is contained. For example, by increasing the initial stirring speed, the particle size of the granulated product becomes smaller.
The initial stirring temperature is usually preferably not too high, and is preferably lower than the boiling point of the specific HFC used. Therefore, in the present invention, the fluoropolymer is stirred in water in a state of containing the specific HFC, and the stirring speed is adjusted at a temperature below the boiling point of the specific HFC in the initial stage to adjust the particle diameter of the granulated product to an optimum size. Then, the temperature is raised and then the stirring treatment is performed while separating the specific HFC, whereby a preferable granulated product having a uniform particle diameter can be efficiently obtained.

[0019]

EXAMPLES [Example 1] Tetrafluoroethylene, ethylene, and (perfluorobutyl) ethylene were added at a charging molar ratio of 4/1 / 0.05.
Copolymerization was performed using C ₄ F ₉ CH ₂ CH ₃ as a polymerization medium.
The charged molar ratio of the monomer / polymerization medium was 2/10. Using 0.09% by weight of perbutyl IB (manufactured by NOF CORPORATION) as a polymerization initiator with respect to the monomer, a copolymerization reaction was carried out at a polymerization temperature of 65 ° C. As a result, the tetrafluoroethylene / ethylene copolymer (copolymer composition,
C ₄ F ₉ CH ₂ CH ₃ containing 8% by weight of tetrafluoroethylene / ethylene / (perfluorobutyl) ethylene = 53/46/1 mol%) was taken out. 500 ml of the mixture of the copolymer and the polymerization medium and 1000 ml of water were charged into a stirring device equipped with 6 turbine blades and 2 baffles, and heated to 90 ° C. at a heating rate of 2 ° C./min. While
The fluorine-containing copolymer was granulated by treating at a rotation speed of 400 rpm for 1 hour. The obtained fluorine-containing copolymer granulated product,
The particle size is about 1.0 mm and the bulk density is 0.65 g / cc
Met. When a plate having a thickness of 5 mm was formed by compression molding at 300 ° C., a clean plate without bubbles could be formed.

Example 2 CF ₃ instead of C ₄ F ₉ CH ₂ CH ₃ as a polymerization medium
Example 1 except that CF (CF ₃ ) CFHCFHCF ₃ was used
Polymerization and granulation were performed in the same manner as in. The obtained fluorocopolymer granulated product had a particle size of about 1.1 mm and a bulk density of 0.45 g / cc. When a plate having a thickness of 5 mm was formed by compression molding at 300 ° C., a clean plate without bubbles could be formed.

Example 3 CF ₃ was used instead of C ₄ F ₉ CH ₂ CH ₃ as a polymerization medium.
Polymerization and granulation were carried out in the same manner as in Example 1 except that CFHCFHCF ₂ CF ₃ was used. The obtained fluorocopolymer granulated product had a particle size of about 1.1 mm and a bulk density of 0.1.
It was 50 g / cc. When a plate having a thickness of 5 mm was formed by compression molding at 300 ° C., a clean plate without bubbles could be formed.

Example 4 (Comparative Example) CF ₃ instead of C ₄ F ₉ CH ₂ CH ₃ was used as the polymerization medium.
Polymerization and granulation were carried out in the same manner as in Example 1 except that CF ₂ CF ₂ CF ₂ CF ₂ CF ₃ was used, bis (perfluorobutyryl) peroxide was used as a polymerization initiator, and the polymerization temperature was 50 ° C. It was The obtained fluorocopolymer granulated product has a particle size of about 0.8 mm and a bulk density of 0.25 g.
/ Cc was low and brittle, and the powder fluidity was poor and it was difficult to handle. Also, since the bulk density is low, 300
Bubbles were present in the molded product when a plate having a thickness of 5 mm was molded by compression molding at ℃.

Example 5 (Comparative Example) 1000 ml of hexane was added to 500 ml of the mixture of the fluorinated copolymer obtained in Example 1 and the polymerization medium, and the mixture was stirred and mixed uniformly, and then mixed using a glass filter. The fluorine-containing copolymer-free portion and the fluorine-containing copolymer-containing portion were separated until the volume of the fluorine-containing copolymer-containing portion was about 300 ml. To the portion containing the fluorine-containing copolymer, 1000 ml of hexane was further added, and the mixture was stirred and mixed uniformly, and the portion containing the fluorine-containing copolymer and the portion containing the fluorine-containing copolymer were again mixed. Separated until the volume was about 300 ml. When this operation was repeated 5 times, about 95% by weight of the polymerization medium in the portion containing the fluorine-containing copolymer was hexane. Then,
Hexane was added to the portion containing the fluorocopolymer to bring the volume to 500 ml, followed by stirring and mixing, and then water 1
000 ml was added and granulation was carried out in the same manner as in Example 1.
However, a powdery fluorine-containing copolymer was obtained without granulation. The bulk density of the powdery fluorocopolymer is 0.15.
It was as low as g / cc, and air bubbles were present in the compression molded product.

[0024]

EFFECTS OF THE INVENTION According to the method of the present invention, a desired fluorine-containing polymer can be produced by using a granulating medium having a much smaller ozone depletion potential with an efficiency comparable to that obtained by using conventional trichlorotrifluoroethane. Granules can be produced.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 48-51084 (JP, A) JP 3-17106 (JP, A) JP 60-44511 (JP, A) JP 3- 176907 (JP, A) Japanese Patent Laid-Open No. 6-298810 (JP, A) Special Table 7-504224 (JP, A) US Patent 3616371 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) C08J 3/00-3/28

Claims (2)

(57) [Claims] 1. A method for granulating a fluoropolymer having a fluoroolefin unit as a main constituent unit, which comprises C ₄ F ₄ H ₄ ,
_{C 4 F 8 H 2, C} 5 F 11 H, C 5 F 10 H 2, C 6 F
_By bringing the fluoropolymer containing a specific hydrofluorocarbon represented by ₁₃ H, C ₆ F ₁₂ H ₂ or C ₆ F ₉ H ₅ into contact with water at a temperature of 20 to 150 ° C. under stirring, A method for granulating a fluoropolymer, comprising separating the hydrofluorocarbon from the fluoropolymer and granulating the fluoropolymer. 2. The production method according to claim 1, wherein the fluoropolymer is a tetrafluoroethylene / ethylene copolymer.